This invention relates to a method for controlling the operation of one or more pumps and to apparatus for carrying out such a method. Although the present invention will be described herein with particular reference to the operation of electrically controlled pumps in a pumping-station, it is not to be construed as being limited thereto. The method and apparatus of the present invention is applicable to any situation in which pumps are used to remove liquid from a vessel in response to an increase in the level of the liquid within said vessel.
A typical pumping-station comprises a plurality of wells or sumps, each well or sump having an inlet to admit liquid thereto and an outlet to remove liquid therefrom. Each outlet is associated with one or more pumps which, in use, transfer the liquid from the well or sump for further processing.
The price of the electricity used to operate the pumps is a significant factor in the cost of running a typical pumping-station. Seasonal (or even daily) variations in tariff costs are implemented by electricity supply companies. It is therefore highly desirable, when operating pumps, to optimise pumping during low-tariff periods and to avoid pumping as much as possible during higher-tariff periods, with the proviso, however, that overflow from the well or pump should if at all possible be avoided.
It may also be required to minimise pumping during certain periods, to avoid noise disturbance caused by the operation of the pumps. For the purpose of the present invention, the period in which it is necessary to avoid the use of the pumps to minimise noise disturbance may be considered to be the same as a higher-tariff period, since the net effect on the operation of the pumps is the same.
Although several methods of controlling the operation of pumps in a pumping-station so as to minimise the consumption of higher-tariff electricity are known (for example GB-B-2298292), such known methods have tended to require a more or less complicated system of plural xe2x80x9con-offxe2x80x9d pumping points and/or means to determine the pumping-rate and running-time of each pump used.
The present invention provides a method of controlling pumps which is based upon the anticipation of a change in the price of the electricity required to operate the pump and which proactively manages the level of the liquid to the optimum, at times of tariff-change.
Accordingly, the present invention provides a method for controlling the operation of one or more electrically-operated pumps to pump a liquid from a well or sump which, in use, receives a substantially continuous inflow of the liquid, wherein the method includes the step of starting or stopping each pump in relation to the approach of a change of tariff for the electricity supplied for the operation of each pump.
Preferably, the method of the present invention includes the steps of providing the customary single set of xe2x80x9cstartxe2x80x9d and xe2x80x9cstopxe2x80x9d points for the pumps associated with each said well or sump and, before actuating the pumps at the xe2x80x9cstartxe2x80x9d point or stopping the pumps at the xe2x80x9cstopxe2x80x9d point, determining the time required to empty and subsequently to refill the well or sump at the current inflow rate and comparing said time with the time remaining before said change of tariff.
For example, if the approaching change of tariff is positive (i.e. the cost of the electricity is about to increase), it is desirable to empty the well or sump completely, prior to the change.
Alternatively, if the approaching change of tariff is negative (i.e. the cost of the electricity is about to decrease), it is desirable for the well or sump to be allowed to fill to an increased level immediately prior to the change.
The present invention also provides apparatus for carrying out the method hereinabove described, the apparatus comprising a well or sump which, in use, receives a substantially continuous inflow of a liquid. The well or sump having an outflow for the liquid and one or more electrically operated pumps associated with the outflow. The well or sump is provided with a single set of xe2x80x9cstartxe2x80x9d and xe2x80x9cstopxe2x80x9d points for the pumps, and further comprising means to determine, at the xe2x80x9cstartxe2x80x9d point and at the xe2x80x9cstopxe2x80x9d point, the time required to empty and subsequently to refill the well or sump and to compare the time with the time remaining before a change of tariff for the electricity supplied for the operation of each pump.
The present invention will be illustrated, merely by way of example, in the following description and with reference to the accompanying drawings.